The invention relates to a jet weaving loom, and especially an air jet loom with pneumatic weft insertion system and an air supply control and regulating system, or pressure controller, for controlling the supply of pressurized air to the main weft insertion nozzles and/or the auxiliary relay nozzles.
In jet weaving looms, and especially air jet looms, it is necessary to achieve a good impulse transfer or kinetic energy transfer from the transport medium such as air to the weft thread. In this regard, the characteristics of the particular thread type of the weft thread being inserted must be taken into account. For example, in connection with a so-called weft mixing in the weft thread insertion process, i.e. a transition from one weft thread type to a different weft thread type, it is known to vary the pressure of the transport medium being supplied to one or more weft thread insertion nozzles, in order to achieve a substantially constant weft thread flight time or transit time of the different thread types through the insertion channel of the weaving reed with a substantially constant rotational speed of the loom. This is important, because a weft thread that reaches the end of the weft thread insertion either too early or too late within a respective weaving cycle can lead to weaving faults.
One known proposal for achieving a constant weft thread flight or transit time for different weft thread types involves allowing so much time for each respective weft thread in a respective weaving cycle, and driving each weft thread with so much transport medium at such a pressure, so that it is practically ensured that both the slowest, as well as the fastest weft thread will be inserted through the insertion channel within the prescribed time window.
Another manner of carrying out the air supply control is that the pressure for all of the main weft insertion nozzles is controlled in common and set to a certain pressure level by a mechanical pressure regulator. Thus, the basic pressure level is first adjusted or set independent of the quality or characteristic differences of the individual weft threads. Additionally, a respective adjustable throttle valve is allocated to each main insertion nozzle, whereby this throttle valve is used to individually adjust and set the particular pressure level required for achieving the prescribed weft thread flight or transit time for this associated weft thread, i.e. respectively for each main insertion nozzle.
The two above-mentioned manners of carrying out the air supply regulation and control are both rather uneconomical with respect to the provision and the consumption of the transport medium, i.e. the compressed air. Moreover, the individual allocation of a respective throttle valve to each respective main nozzle, and further to each respective so-called tandem main nozzle if the loom needs to be equipped with such tandem main nozzles, is rather costly, complicated, and time consuming with respect to the structural and installation effort of the control and regulating system, and with respect to the individual adjusting of the respective blowing air pressures at the respective throttle valves.
German Patent 30 43 003 discloses an air jet loom that is equipped with a measuring arrangement for measuring the transport velocity of the inserted weft thread, and with a control system in which a signal representative of the thread transport velocity is converted into a control signal, which in turn is used to influence or control the components of the weft thread insertion system that determine the insertion velocity of the weft thread. A person of ordinary skill will recognize from this German Patent, that the weft thread insertion system includes the main weft insertion nozzles, and that a pressure control or regulating valve is respectively allocated to each main nozzle.
In view of the above, it is an object of the invention to provide a control and regulating system for the pressurized fluid supply for the main weft insertion nozzles, and for the tandem main weft insertion nozzles when applicable, that is simple in its structure, operation, and maintenance, economical in its original manufacturing and installation costs, economical in operation with respect to the consumption of pressurized fluid medium, and also rapidly reacting, so that it can achieve the required pressure already at the start of the loom for the first weft thread insertion, as well as achieving any desired varied pressure level from one weft insertion to the next. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a control arrangement for controlling the supply of air to plural main weft insertion nozzles of an air jet loom. Each main nozzle can include a single main nozzle or tandem main nozzles. The overall air supply arrangement includes a pressurized air source, and a control and regulating system (also called a pressure controller herein for simplicity and brevity) interposed and connected between the pressurized air source and the main weft insertion nozzles.
Especially according to the invention, the control and regulating system for all of the main weft insertion nozzles includes only one single multi-path servovalve with an integrated pressure sensor and pressure regulation and control electronics. Particularly, the multipath servovalve may be any conventionally known 3/2 way or multipath servovalve, e.g. having a solenoid or other electromagnetic actuator. The pressure regulation and control electronics receive a control signal from an external controller. The pressure regulation and control electronics compare a measured pressure signal corresponding to the actual pressure measured downstream from the multipath servovalve, with the control pressure indicated by the external control signal. Responsive to any difference or deviation between the actual pressure and the desired control pressure, the pressure regulation and control electronics actuate the multipath servovalve to connect either the pressurized air source, an air vent, or a closed connection, with a main pressure line on the side of the multipath servovalve toward the main weft insertion nozzle arrangements, so as to regulate the actual pressure provided in this main pressure line to correspond to the desired control pressure. The electronics may comprise any hardware and/or software for receiving and comparing the actual pressure signal and the control pressure signal, e.g. including an amplifier, a comparator, etc.
According to further preferred embodiment features of the invention, the external controller provides the external control signal in consideration of or based on the measured actual value of the actual weft transport flight or transit time or the corresponding rotational angle of the loom main drive shaft, which actual value is compared with a prescribed nominal or rated value, whereupon the determined time or rotational angle difference is converted into the external control signal. Thereby, the pressure to be provided to the main weft insertion nozzles is adjusted to speed-up the weft insertion if the actual measured weft insertion was too slow, or to slow-down the weft insertion if the actual measured weft insertion was too fast.
Further preferably according to the invention, a pressure distributor (i.e. plenum or manifold) is connected to the main pressure line that extends from the output of the multipath servovalve of the pressure control and regulating system. In turn, plural respective secondary pressure lines branch off from the pressure distributor or manifold and lead individually to the plural main weft insertion nozzles. A respective individual servo shut-off valve is interposed in each of the individual secondary pressure lines. Thus, the multipath servovalve of the pressure control and regulating system sets the pressure being supplied to the pressure manifold, and the individual servo shut-off valves respectively individually control which weft insertion nozzle or nozzles will receive the pressurized air at the respective instantaneously prevailing pressure in the pressure manifold at any given time.
The inventive use of a single multipath 3/2 way servovalve with an integrated pressure sensor and pressure regulation and control electronics now advantageously makes it possible to adjust and set the pressure level of the pressurized air that will be supplied respectively to each individual main weft insertion nozzle in a direct manner, i.e. without requiring individual mechanical adjustment for each respective main nozzle arrangement via the control software of the air jet loom. Also, the system is substantially simplified in comparison to the prior art, because it is no longer necessary to provide the conventionally known allocation of a respective pressure control valve or throttle valve for each individual main nozzle or each tandem main nozzle, but instead to provide a single valve, which is able to switch from one pressure level to another pressure level in only a few milliseconds, for example within about 15 to 20 ms for switching from a first required pressure level of e.g. 2.5 bar to a second required pressure level of e.g. 5.0 bar. Thereby, it is possible to adjust the pressure level individually and successively for each weft insertion nozzle and for each successive weft insertion. The invention makes use of the fact that only one particular pressure level will be needed at any particular instant in time, regardless of how many total weft insertion nozzles are provided, for example for different selectable weft thread colors or thread qualities.